1. Field of the Invention
The present invention relates to a process for converting olefinically unsaturated compounds to their corresponding diols or polyols in the presence of a specifically defined oxidation catalyst composition, water, and an oxygen containing gas.
2. Description of the Prior Art
Processes for the production of glycols, such as ethylene glycol, from olefins are well known in the art. One class of these processes involves the conversion of an olefin, e.g., ethylene, to its corresponding oxide, e.g., ethylene oxide, as an intermediate. This intermediate is subsequently hydrolyzed to form the corresponding glycol. Prominent in this class of processes is a method wherein an olefinic compound is reacted with an organic hydroperoxide compound in the presence of a molybdenum catalyst to form the corresponding oxide. The organic hydroperoxide preferably is formed by reacting an aliphatic saturated compound with oxygen. The reaction scheme can be summarized as follows: ##STR1## The commercial attractiveness of this process is dependent on the ability to use or sell the organic alcohol co-product. Given the fluctuation in economic conditions, however, it may be difficult to dispose of large quantities of these organic alcohol co-products in an economically attractive manner. In any event, it can be troublesome, when the quantity of one product, selected on the basis of marketing possibilities for a given period, necessarily determines the quantity of some other product which may be smaller or larger than desirable in view of changing marketing requirements within that same period. It can, therefore, under certain circumstances be considered as a disadvantage of the aforenoted process that such large quantities of organic alcohols are formed as co-products, even though under other circumstances the formation of two products may well be found acceptable.
An alternative multi-stage method for making ethylene glycol involves the oxidation of ethylene to ethylene oxide at elevated temperatures and pressure using oxygen and a silver containing catalyst. The ethylene oxide is then hydrated either catalytically using a diluted aqueous solution of a strong acid, or at high temperatures and pressures, with some diethylene and triethylene glycols being formed as by-products. Because, in the first reaction stage (i.e., ethylene to ethylene oxide) one molecule of oxygen theoretically forms one molecule of carbon dioxide from the ethylene, the maximum theoretical selectivity of this reaction is at best 85%. Moreover, the first stage of reaction requires very careful control of the operating conditions just to obtain selectivities in the range of 60 to 70%. Thus, rigid process control and by-product formation are disadvantages of this type of indirect glycol formation.
An alternative approach to glycol formation involves the catalytic oxidation of olefins directly to form the corresponding glycol without the formation of olefin oxide intermediates.
For example, it is well known from the technical literature and patents that olefins can be effectively directly oxidized with a strong oxidizing agent in the presence of catalytic amounts of osmium oxides, e.g., osmium tetroxide, e.g., to their corresponding glycols.
More specifically, Japanese Patent Application No. Sho 54-145604, published Nov. 14, 1979, is directed to a process for hydroxylating olefins in the presence of OsO.sub.4, a quaternary ammonium salt such as tetra ethyl ammonium bromide, and a peroxide including organo peroxides and H.sub.2 O.sub.2 as the oxidant. The use of oxygen as the oxidant is not disclosed nor is the co-presence of co-catalyst I salts as described herein disclosed. Selectivities to glycol of from about 4.5 to about 66% are disclosed. H.sub.2 O.sub.2 oxidant in combination with OsO.sub.4 is known as Milas reagent which can lead to non-selective oxidation of olefins as well as over oxidation. H.sub.2 O.sub.2 is also substantially more expensive than oxygen or air. Accordingly, the uses of organohydroperoxides as well as H.sub.2 O.sub.2 as oxidants are each associated with their own disadvantages.
U.S. Pat. No. 2,414,385 discloses the use of hydrogen peroxide and a catalytically active oxide, such as osmium tetroxide, dissolved in an essentially anhydrous, non-alkaline, inert, preferably organic, solvent, to convert, by oxidation, unsaturated organic compounds to useful oxygenated products such as glycols, phenols, aldehydes, ketones, quinones and organic acids. The formation of glycols is achieved by conducting the reaction at temperatures of between several degrees below 0.degree. C. and 21.degree. C. Such low reaction temperatures drastically and disadvantageously, reduce the reaction rate to commercially unacceptable levels. At temperatures greater than 21.degree. C., the formation of aldehydes, ketones, and acids is favored.
U.S. Pat. No. 2,773,101 discloses a method for recovering an osmium containing catalyst such as osmium tetroxide, by converting it to the non-volatile osmium dioxide form, distilling the hydroxylation product, re-oxidizing the osmium dioxide to the volatile osmium tetroxide, and then recovering the same by distillation. Suitable oxidizing agents used to oxidize olefins, and re-oxidize the osmium dioxide, include inorganic peroxides such as hydrogen peroxide, sodium peroxide, barium peroxide; organic peroxides, such as t-butyl peroxide or hydroperoxide, benzoyl peroxide; as well as other well known oxidizing agents such as oxygen, perchlorates, nitric acid, chlorine water and the like. As with other methods of the prior art, the above process yields undesirable by-products (see col. 1 line 55) thus reducing the selectivity of the process.
British Patent Specification No. 1,028,940 is directed to a process for regenerating osmium tetroxide from reduced osmium tetroxide by treatment of the latter with molecular oxygen in an aqueous alkaline solution. More specifically, it is disclosed that when osmium tetroxide is used by itself as an oxidizing agent, or as a catalyst in conjunction with other oxidizing agents, to oxidize hydrocarbons the osmium tetroxide becomes reduced, and in its reduced form is less active than osmium tetroxide itself. Consequently, by conducting the oxidation reaction in the presence of an alkaline medium and supplying oxygen to the medium throughout the process, the osmium tetroxide is maintained in a high state of activity. The oxidation products disclosed include not only ethylene glycol from ethylene but also organic acids from said compounds as vicinal glycols, olefins, ketones, and alcohols. While the pH of the alkaline medium is disclosed broadly for all possible reactions as varying from 7.5 to 12 for purposes of reoxidizing reduced osmium tetroxide, the pH employed in the example for preparing ethylene glycol is 9.5. If the pH is too high, a wide variety of products is produced as a result of over oxidation and/or degradation. Thus, the sensitivity of the process to the pH of the medium necessitates rigid pH which is economically disadvantageous.
U.S. Pat. No. 4,255,596 is directed to a process for preparing ethylene glycol in a homogeneous single-phase reaction medium using ethylbenzene hydroperoxide as the oxidizing agent dissolved in ethylbenzene and osmium tetroxide as the catalyst. The pH of the reaction medium is maintained at about 14 by the presence of tetraalkyl ammonium hydroxide. A small amount of water can dissolve beneficially in the medium to reduce by-product formation and improve selectivity to the glycol.
U.S. Pat. No. 4,049,724 describes the preparation of glycols from alkenes and from unsaturated alcohols in an aqueous system using osmium tetroxide and specifying stable and water-soluble aliphatic hydroperoxides, such as tert-butyl hydroperoxide, while a critical pH of 8 to 12 is maintained by a suitable combination of alkali metal buffering compounds. The preparation of propylene glycol utilizing tert-butyl hydroperoxide is exemplified in the patent at a selectivity based on the hydroperoxide of 45 percent.
None of the aforenoted patents disclose the osmium containing-co-catalyst system described herein.
See also: U.S. Pat. No. 3,317,592 (production of acids and glycols using oxygen as oxidant, OsO.sub.4 as catalyst at pH 8-10); U.S. Pat. No. 3,488,394 (discloses hydroxylation of olefins by reacting olefin and hypochlorite in the presence of OsO.sub.4); U.S. Pat. No. 3,486,478 (discloses reaction of hypochlorite and olefin in an aqueous medium and in the presence of OsO.sub.4 catalyst to hydroxylate the olefin); U.S. Pat. No. 3,928,473 (hydroxylation of olefins to glycols with O.sub.2 oxidant, octavalent osmium catalyst (e.g., OsO.sub.4), and borates as promoter); U.S. Pat. No. 3,931,342 (discloses a process for recovering glycols from an aqueous solution containing alkali metal borate and osmium compounds (e.g., OsO.sub.4); U.S. Pat. No. 3,953,305 (discloses use of OsO.sub.4 catalyst for hydroxylating olefins which is regenerated by oxidizing hexavalent osmium with hexavalent chromium and electrochemically regenerating hexavalent chromium); U.S. Pat. No. 4,203,926 (discloses ethylbenzene hydroperoxide as oxidant used in two phase system to hydroxylate olefins in presence of OsO.sub.4 and cesium, rubidium and potassium hydroxides); U.S. Pat. No. 4,217,291 (discloses the oxidation of Osmium (III) or (IV) in an ionic complex with oxygen and an alkali metal, ammonium, or tetra (-lower) alkyl ammonium cation to a valency of greater than +5+organo hydroperoxides); and U.S. Pat. No. 4,229,601 (discloses the use of cesium, rubidium and potassium hydroxides as promoters for OsO.sub.4 catalyst and t-butyl hydroperoxide oxidant for hydroxylating olefins).
None of the aforenoted patents disclose the catalytically active metal oxide-co-catalyst I system described herein either alone or in combination with at least one co-catalyst II described herein.